A storage system having an encryption function is used to protect the secrecy of data. Storage systems having an encryption function encrypt the write data sent from a higher-level device such as a host computer, and save the same in a storage device. Encryption is generally performed using a data encryption key. If the encryption key is changed incorrectly due to failure or the like, encrypted data cannot be decrypted, so that the data is actually equivalent to being lost.
Patent Literature 1 discloses a disk drive for encrypting and storing data, and in the disk drive, only the latest encryption key used currently is saved in an internal memory, and during write operation, data including a key generation information of the encryption key is written in the disk. During the read operation, the key generation information included in the data is checked, and if the key generation information is the latest information, the data is decrypted using the encryption key saved in the memory of the storage device.